1. Technical Field
The invention relates to magnet temperature estimation for permanent magnet (PM) electric machines based on magnetic flux linkage. The invention further relates to hybrid electric vehicles that use permanent magnet (PM) motors.
2. Background Art
The use of permanent magnet (PM) synchronous motors has become widespread. In general, a PM synchronous motor includes a rotor having permanent magnets mounted on the rotor periphery or buried inside the rotor.
It is difficult to measure the temperature of magnets buried deep in the rotor of an electric machine. An infrared sensor can only sense the temperature of the rotor surface but magnet temperature can get much higher than surface temperature. Inductive heating to the magnets and air conduction at the surface can significantly increase the difference between magnet temperature and rotor surface temperature. A wireless sensor could be used for large industry motors but a wireless sensor is not cost effective on applications such as hybrid electric vehicles.
For the foregoing reasons, there is a need for a method of estimating magnet temperature for permanent magnet (PM) electric machines.